This invention relates to a raised panel door, and more particularly, to a construction for such a door which enables the manufacture of doors having enhanced fire-resistant properties, whereby the doors may be employed in building installations where strict fire code regulations are applicable.
A conventional panel door comprises what are known as stiles and rails extending vertically and horizontally in the door. The rectangular spaces which are bounded by these stiles and rails are filled with panels, and these normally have tapered marginal edges which seat within grooves presented by the stiles and rails. A panel door of this description typically may be made of a decorative wood, such as oak, etc., and because of its esthetically pleasing appearance, is widely sold.
While a conventional door has a pleasing appearance, because of its material content and structure, the door suffers durability, security and safety problems that detract from its utility. Under the stress of normal usage and the passage of time, the stiles and rails tend to sag, warp and split, or otherwise separate from each other, with loosening of the panels which they encompass. The door provides a relatively poor barrier to the transmission of sound and offers little resistance to fire. More recently, doors have been proposed which feature what is referred to herein as a continuous core forming the midregion of the door, and overlays and/or panel inserts positioned over opposite sides of the door which impart to the door the appearance of a traditional panel door. Exemplary of such constructions are the constructions discussed in my prior U.S. Pat. Nos. 4,702,054 and 4,756,350.
In constructing a door intended to have a fire rating conforming to rigorous standards, as required presently in many constructions, such as offices, hotels, etc., the use of a core composed of a compacted mineral-based material would be advantageous because of such material's extremely high resistance to fire. It is not uncommon, for instance, for a door that is to meet rigorous specifications, that it withstand a temperature in the range of 1600.degree. F. for an hour without burn through. However, another test to which a door may be subjected is known as a hose stream test, where the door after heat exposure is subjected to a stream of water projected thereat at, for example, 80 pounds per square inch through an inch line placed 20 feet from the door. While a compacted mineral-based mineral may have requisite fire-resistant properties, it has a crumbly consistency and tends to decrease in strength when subjected to a prolonged high temperature. As a consequence, the construction of a fire-resistant door using such a material, and where the door must meet severe standards, presents problems.
According to this invention, a raised panel-style door is contemplated, where overlays are applied to opposite sides of the door, in those regions which simulate the stiles and rails of the door, and these overlays are relied upon to provide strength to the door and as a means for securing an overlay or panel insert present in the door in a panel-simulating zone of the door.
More specifically, this invention contemplates the incorporation of molding strips in the door which, in cross section, have a lower level surface and spaced laterally therefrom, an upper level surface, with the body of a molding strip providing a bridge spanning these two surface levels. The molding strips are applied to the door with their lower level surfaces against an overlay or panel insert, as the case may be, in a panel-simulating zone of the door, and their upper level surfaces secured to the overlay which forms a face of the door.
In meeting more restrictive fire standards, the percentage of the face of the door which is taken up by the stile- and rail-simulating regions plays a part, since the stile- and rail-simulating regions generally are of greater thickness than portions of the door in a panel-simulating zone, which might be recessed inwardly into the door to produce the panel simulation, these recessed regions being located opposite each other in the door and cumulatively having the effect of reducing the thickness of the door where they appear. Following the invention, a fire-resistant material, such as a compacted mineral-based material, may be used essentially entirely throughout the width of the door in stile- and rail-simulating regions, with the molding strips contemplated providing a means for adhering overlays applied to the door in the stile- and rail-simulating regions.